Process for refining mineral oils



Patented Jan. 2, 1940 UNITED STATES PATENT OFFICE PROCESS FOR REFININGMINERAL OILS No Drawing.

Original application November 6,

1933, Serial No. 696,910. Divided and this application January 19, 1938,Serial No. 185,690. In the Netherlands July 23, 1928 8 Claims. (01.196-13) This invention relates to extraction methods of refining mineraloils, and is particularly concerned with methods for extracting suchoils by means of a selective solvent in the presence of chloroform. Thisapplication is a division of our application, Serial No. 696,910, filed.November 6, 1933, on which Patent No. 2,124,606 was issued July 26,1938.

It has been known in the art that crude petroleum oils, lubricating,transformer and spindle oils, kerosenes, heavy or light naphthas, etc,can

be separated into groups of components by ex-- traction with suitableselective solvents. A large number of such solvents are available forthe purpose. The present invention is particularly (but not exclusively)directed to an improvement in methods of extracting mineral oils withfuriural or acetone, which improvement is analogous to the one claimedfor S02 in Patent No. 1,945,516, which issued upon our application,Serial No. 379,310, filed July 18, 1929, of which this is acontinuation-in-part.

The invention is based on the discoverythat the extractioncharacteristics of substantially any solvent which is capable ofseparating a mineral oil into two component groups-one more solubletherein than the other-can be markedly modified by introducingchloroform into the extraction mixture.

The type of selective solvents whose efiectiveness as the extractingagents in refining mineral oils can be improved by practicing thisinvention is illustrated by liquid S02, furfural, and acetone. Thesespecific examples represent, however, only typical solvents of a largenumber of known selective solvents capable of separating mineral oilsinto aromatic and non-aromatic components (sometimes referred to asnaphthenic and paraffinic or as non-paraffinic and parafiinic) whichsolvents are intended to be within the scope of this invention.

Likewise, the auxiliary solvent, whose presence in the extractionmixture improves the efficacy of extraction consists predominantly ofchloroform, i. e., it may consist entirely of chloroform or it maycontain chloroform in admixture with minor proportions of such relatedsolvents as ether, benzol or toluol, or with a relatively volatileliquid chemically or physically related to benzol, such as aromatichydrocarbons, which related solvents usually are miscible in allproportions with the main solvent and can be relatively easily separatedfrom the material being treated, for example by distillation, and haveno detrimental efiect on the refined products.

It will be understood, therefore, that the pres ent invention is toinclude within its scope the extraction processes employing a selectivesolvent which may be a single substance or a mix: ture of suitablesubstances) and wherein extrac- 5 tion is carried out in the presence ofan auxiliary solvent consisting predominantly of chloroform and havingan action similar to that of benzol,

i. e., causing an increase in the efficiency of separating a mineral oilinto its components, 10 which may be the naphthenic and parafiinicportions of the oil.

Generally speaking, the efficiency of extraction is determined by thesolvent power and the selectivity of the solvent (or solvent mixture)with 16 regard to the components oi the mixture being extracted. Theefiiciency may be measured by and compared with the relative yields ofthe raffinate of the desired purity in cases where the mass or volume ofthe main or selective solvent is -20 kept constant.

If the extraction efficiency is to be compared in cases where therelative yield is fixed, whilst also the mass or volume of the main orselective solvent is kept constant, then the quality of the 25 rafiinatemay be taken as the measure of the efficiency. i

The efficiency of the various extractions may also be measured bycomparing the extent to which the solvent is conserved, if the same raf-30 finate is made with or without the useof the auxiliary solventdescribed in this specification.

By applying this invention, i. e., by using a main solvent in thepresence of an auxiliary solvent, it becomes possible, therefore, inextracting .35 hydrocarbon oils to improve the quality and/or quantityof the raffinate and/or to conserve the main solvent.

The method of this invention also provides a means for improving mineraloils having rela 40 tively low contents of naphthenic (aromatic)components, which contents it is difficult or impossible to reducestillfurther by extraction with the main solvent alone.

The improved qualities of the raflinate may be 45 controlled, e. g., bydetermining the viscosity index, the no, or refractive index, or thestability against oxidation. All these properties are dependent on theratio between aromatics (nonparaii'ins) and the parafiins.

The increased extraction efficiency of the mixed solvent process, ascompared with the efficiency of the corresponding single solventprocess, is apparently due to the favourable eifect of the mixed solventon the distribution ratios of 55 the non-paraffinic and parafliniccomponents of the oil in the extract and raflinate phases; in otherwords, the content of the components pref erentially soluble in theselective solvent as compared with that in the rafiinate phase isincreased in the presence of the auxiliary solvent, so that when a mixedsolvent is used it becomes possible sometimes, under suitabletemperature conditions, to produce from an oil a greater quantity of theraihnate, which is richer in parafiinic components than it would havebeen possible to obtain if only the main solvent were used.

From the nature of the auxiliary solvents it may be seen that theiraddition to the main solvent would normally produce a solvent mixturewith a greater solvent power for the oil than that of the main solvent,so that the selectivity of the solvent and the yield of the rafilnatemay be impaired, Although this is not necessarily a disadvantage, as amain solvent with an auxiliary solvent added thereto in any case will beuseful in increasing the extraction efiiciency so far as the quality ofthe rafiinate is concerned, it is possible to improve this impairedselectivity by suitably lowering the temperature of extraction with theresultant additional increase in the, efficiency of extraction so faras, e. g., the yield of the rafiinate is concerned. In general, theextraction temperature is so selected as to create optimum conditionsfrom the view points of' economy, yield, purity of the products, etc.

The operating details of putting the invention 1 into practice, such astemperatures, pressures, etc., may vary in different cases, dependingupon specific properties of the substances used in each case, or may becontrolled by some other consideration. For example with a so-calledbatchextraction the auxiliary solvent may be mixed with the oilundergoing treatment either before, or at the time the oil is contactedwith the main solvent; the whole or a part of the auxiliary solvent maybe mixed with the main solvent prior to contacting it with the oil.

It is preferable, although not necessary, to operate the process of thisinvention in a continuous countercurrent manner, i. e., passing the mainsolvent countercurrently to and in contact with the oil being extractedthrough a mixingse-ttling zone and adding at least a portion of theauxiliary solvent to the oil-main solvent mi;- ture at a point, orpoints, along the mixing-settling zone, and preferably at such a placewhere such an addition of the auxiliary solvent would be most eifective.The extract and raifinate phases are separated, usually by gravity, andthe main and auxiliary solvents or the main solvent only are thenremoved from each of the phases by distillation (both solvents beingremoved together or in separate stages) or by some other suitable means.The separated solvents may be continually reused. The auxiliary solventmay be left in the raffinate if this solvent improves the quality of theraffinate, e. g., its anti-knock property in case of the extraction ofrelatively heavy hydrocarbons with the aid of benzol as a constituent ofthe auxiliary solvent.

In order to demonstrate the effectiveness of the new process thefollowing example may be set forth.

A number of samples ofa lubricating oil having viscosity index 59(indicating that the oil had a relatively high content of aromatics or alow content of parafiinic hydrocarbons) were thoroughly contacted withvarious quantities of furfural, of furfural-benzol, and offurfuralchloroform mixtures; in each case the raflinate (upper) layerswere separated, and the viscosity and refracting indices of solvent-freeportions (rafiinates) were determined. The following table contains thepertinent data:

These results show that the presence of an auxiliary solvent, such asbenzol, or chloroform,

causes a marked improvement in the refined product; the results alsodemonstrate that non-parafiinic components are extracted in preferenceto parairlnic components when furfural-benzol mixture is used instead offurfural alone.

The following example further illustrates some of the effects ofextraction temperature upon the efficiency of extraction when a motoroil having a viscosity index -5 is extracted.

Fur- Ben- Ohloro- Tempem' Ramnate Oil ture of arts fuml Z01 form Extracpparts parts parts tion 00 Percent Viscosity yield index These datademonstrate that the yield and the degree of refinement of the rafiinatemay be controlled at will by regulating the extraction temperature andthe relative quantity and the composition of the mixed solvent, and theselective solvent can be conserved, when used with an auxiliary solventfor producing the raffinate having a fixed viscosity index.

Similar results may be obtained when extracting mineral oils with otherselective solvents, such as acetone, in the presence of an auxiliarysolvent containing a predominant quantity of chloroform.

It has been also found that various mixtures of selective solvents,such, for example, as liquid SOs-flil'flll'tl, can be successfully usedfor extracting mineral oils in the presence of either chloroform or itsmixtures with solvents or the type of benzol, as outlined heretofore.

While it is practical and may be desirable in some cases to carry outthe extraction of mineral oils by means of the main and auxiliarysolvents at such temperatures, at which the auxiliary solvent is onlypartially soluble in either the main solvent or the oil being extracted,or in both, it should be noted that the extraction. process of thisinvention may be operated at the temperatures at which the auxiliarysolvent becomes miscible in all proportions with either the main, i. e.,selective, solvent or the oil, or both.

The main solvents used in this extraction process to separate a mineraloil into two component groups as defined, have the common characteristicthat, like liquid S02, acetone or furfural, at the extractiontemperature they are completely miscible only with the non-paraffiniccomponent group. With the parafiinic component group they are miscibleonly to a limited extent. Examples of suchlike selective solvents are:nitromethane, propionitrile, dimethyl sulphate, dimethyl sulphite,methyl formiate and several alcohols or esters at suitable temperatures.

With reference to what has been stated above in respect to the auxiliarysolvents, it deserves notice that the particular effect of auxiliarysolvents on the extraction efficiency is independent of the phenomenonof dilution of the mixture being extracted, which dilution may or maynot take place, depending upon viscosities of theliquids involved.Therefore, the process is elfective not only with oils which may beviscous at extraction temperatures, but also with oils which are easyflowing or non-viscous at such temperatures. For example, when liquidS02 is used as 2! selective solvent, the extraction temperatures arerelatively low, so that certain viscous oils may have to be diluted withlight solvents, while less viscous oils can be extracted without beingpreviously diluted. On the other hand, oil which may be regarded asbeing viscous at ordinary temperatures (say, over 80 seconds at 100 F.Saybolt Universal) would become easy flowing at the slightly elevatedtemperatures of extraction with furfural, for example, or some otherselective solvent, so that their dilution for the purpose of reducingthe viscosity would be unnecessary. The use of auxiliary solvents inthese cases would serve only the purpose of improving the extractionefficiency through the effect of such solvents on the distribution ofthe components being extracted between the extract and rafrlnate phases,no dilution being necessary.

We claim as our invention:

1. In an extraction process for separating hydrocarbon oils intoportions of different degrees of parafiinicity, the steps of bringing aliquid hydrocarbon oil into contact with a selective solvent fornon-parafiinic hydrocarbons in the presence of chloroform, underconditions causing the formation of liquid extract and raffinate phasesand separating the phases.

2. The process according to claim 1, wherein the oil is a minerallubricating oil.

3. In an extraction process for separating hydrocarbon oils intoportions of different degrees of paraffinicity, the steps ofcounterflowing' under extracting conditions streams of a liquidhydrocarbon oil fraction and a selective solvent for non-paraflinichydrocarbon components of the oil, in the presence of chloroform,thereby forming liquid rafiinate and extract phases, and separating saidphases from each other.

4. In an extraction process for separating lubricating mineral oils intoportions of dilIer-ent degrees of paraffinicity, the steps ofcounterfiowing under extracting conditions concurrent streams ofchloroform and a selective solvent for non-parafiinic hydrocarboncomponents of the oil, and a stream of liquid lubricating oil, therebyforming liquid rafiiuate and extract phases, and separating the saidphases.

5. In an extraction process for separating a hydrocarbon oil intoportions having different degrees of paraiiinicity, the steps ofbringing a liquid hydrocarbon. oil into contact with furfural in thepresence of an auxiliary solvent consisting predominantly of chloroform,under conditions causing the formation of liquid raffinate and extractphases, separating the said phases, the temperature of contact beinglower than that required to produce a raflinate phase of the samequantity with the same relative quantities of furfural and oil in theabsence of the auxiliary solvent. l

6. In an extraction process for separating a hydrocarbon oil intoportions having different degrees of paraffinicity, the steps ofbringinga liquid hydrocarbon oil into contact with acetone in thepresence of an auxiliary solvent consisting predominantly of chloroform,under conditions causing the formation of liquid raffinate and extractphases, and separating the said phases, the temperature of contact beinglower than that required to produce a raffinate phase of the samequantity with the same relative quantities of acetone oil in the absenceof the auxiliary solvent.

'7. In an extraction process for separating a hydrocarbon oil intoportions having different degrees of paraiiinicity, the steps ofbringing a liquid hydrocarbon oil into contact with sulfur dioxide inthe presence of an auxiliary solvent consisting predominantly ofchloroform, under conditions causing the formation of liquid raftinateand extract phases, and (separating the said phases, the temperature ofcontact being lower than that required to produce a raffinate phase ofthe same quantity with the same relative quantities of sulfur dioxideand oil in the absence of the auxiliary solvent.

8. In an extraction process for separating a hydrocarbon oil intoportions having difierent degrees of paraflinicity, the steps ofcontacting a stream of liquid hydrocarbon oil countercurrently with astream of a selective solvent for non-paraffinic hydrocarbons underconditions causing the formation of liquid raifinate and extract phasesin the presence of an auxiliary solvent ccnsisting predominantly ofchloroform, a portion only of said auxiliary solvent being initiallyintroduced into the counterflowing streams with the fresh selectivesolvent, and another portion being introduced into said streams at apoint spaced from the point of introduction of the selective solvent inthe direction of thepoint of introduction of the initial oil, andseparating said phases, the temperature of the process being lower thanthat required to produce a raiiinate phase of the same quantity with thesame relative quantities of selective solvent and oil in the absence ofthe auxiliary solvent.

JOHANNES ARNOLDUS BUCHEL. REYERUS NICOLAAS JAN SAAL.

